The present invention relates to a manufacturing method for flanged resin products and a flanged resin product, and particularly, to a manufacturing method for flanged resin products in which, after a plurality of separate pieces including a flanged separate piece are molded by a primary injection of a resin, the plurality of separate pieces are joined together to mold a resin product by a secondary projection of a welding resin, and to a flanged resin product formed by the same.
As a manufacturing method for resin products, there is known an injection welding method in which separate pieces, or the like, obtained by a blow molding, or injection molding, are covered and joined by a molten resin.
As such an injection welding method, there is proposed a so-called DSI (die slide injection) method, or DRI (die rotary injection) method.
In the DSI method, in general, after a set of primary mold products are obtained by an injection molding using a set of dies, one die is moved relative to the other to bring end faces of the set of primary mold products into abutment, and a molten resin is injected in a periphery of the abutting parts, joining them both together to manufacture the set of primary mold products as a complete article.
In the DRI method, in general, a set of relatively rotatable dies are used, and per every rotary action, obtaining a set of primary mold products by an injection molding, end faces of the set of primary mold products are brought into abutment, and a molten resin is injected on a periphery of the abutting parts, joining them both together and thus, manufacturing the set of primary mold products as a complete article.
On the other band, most resin products are provided with flanges such as joints, with opponent parts to be molded.
A study by the present inventors however shows that, in the case a resin product is provided with a flange as above, it is preferable to provide in a die a gate for injecting a molten resin to mold the flange.
For example, an intake manifold, which is made of resin, of an automobile engine is now examined as a flanged resin product. In a case where such a resin made intake manifold is molded by an injection welding molding method, or more specifically, in a case where a plurality of separate pieces, including a flanged separate piece, are simultaneously molded in a primary injection molding phase, there can be assumed an arrangement in which a gate for molding the flanged separate piece is laterally provided to a periphery of a flange.
For such a case, an additional study by the present applicants shows that molten resin has a reduced tendency to flow opposite the gate, with a resultant limit to molding precision; for example, a flange dimension.
In particular, such a flange generally constitutes a joint with an opponent part, such as a surge tank, and requires the joint to have a necessary flatness, or area, to be sufficiently and accurately secured as a base. In addition, fine configurations, such as an O-ring fitting groove to be simultaneously formed along the flange to provide a secure sealing, are required to be well secured with a sufficient precision.
The present invention is made on the basis of such studies, and it is an object of the invention to provide a manufacturing method for a resin product having a flange, and a resin product having a flange, allowing for a flanged separate piece to be molded, without reduction in accuracy of flange dimension, in a primary injection molding phase.
Accordingly, there is provided an manufacturing method for a resin product having a flange an in particular, a manufacturing method for a resin product comprised of a plurality of separate pieces and having a flange. The plurality of separate pieces include one, as a separate piece, having a flange corresponding to the flange of the resin product, and the plurality of separate pieces, including the separate piece having the flange, are primary-injection-molded by a primary injection of a resin, and respective separate planes of the plurality of separate pieces are in abutment, joining the separate pieces together. The resin product having the flange is molded by a secondary injection of a welding resin. When molding the plurality of separate pieces, including the separate piece having the flange, by the primary injection of the resin, a gate part, to which molding material is injected for molding the flange of the separate piece having the flange, is positioned inside the flange to be part of the flange.
Additionally, a resin product having a flange, according to the invention, is molded by this method.